There has been known an apparatus for acquiring a tomographic image of an eye to be inspected using optical coherence tomography (OCT) (also called OCT apparatus). A field angle is limited because of aberrations caused by optical members of the apparatus, and hence there is a limitation on a region on which imaging can be performed at a time. When a position of a fixation lamp to be turned on is adjusted, a line of sight of an eye to be inspected may be shifted. Therefore, when imaging is performed multiple times while the position of the fixation lamp to be turned on is adjusted, a fundus of the eye to be inspected may be imaged in a large region. During the imaging, when the line of sight is shifted while a cornea of the eye to be inspected is irradiated with a measuring beam, there is a possibility that the measuring beam is blocked by an iris of the eye to be inspected. In this case, the fundus is not irradiated with the measuring beam, and hence a suitable tomographic image cannot be acquired. Thus, PTL 1 discloses a fundus camera in which an optical axis of an optical system is shifted so as to align with an eye axis of the eye to be inspected based on the position of the fixation lamp to be turned on. This fundus camera ensures that the measuring beam is not blocked by the iris of the eye to be inspected, and hence a clear fundus image may be acquired.
PTL 2 discloses an OCT apparatus in which an arbitrary position of a tomographic image displayed on a display unit is specified and an optical path length of a reference beam is changed based on the specified position. This OCT apparatus ensures that an imaging position of the eye to be inspected in a depth direction (optical axis direction) thereof is adjusted.